Equilibrium constants sodium sulfate complexes

In what follows, one considers for illustration purposes the case in which the charge is generated on the surface of colloidal particles or droplets by the adsorption of a surfactant, namely sodium dodecyl sulfate (SDS). We selected this case because information about the adsorption of SDS on an interface is available in the literature, and as it will become clearer later the number of parameters involved is smaller than in the case of silica. A more complex calculation about the silica and the amphoteric latex particles will be presented in a forthcoming paper. It involves several kinds of surface dipoles and equilibrium constants. 

An ionic achiral micelle [e.g., sodium dodecyl sulfate (SDS)] and a neutral CD are typically used as a pseudo-stationary phase and a chiral selector, respectively. When a pair of enantiomers is injected into this system, two major distribution equilibria can be considered for the solutes or enantiomers (a) the equilibrium between the aqueous phase and the micelle (i.e., micellar solubilization) and (b) the equilibrium between the aqueous phase and CD (i.e., inclusion complex formation). Each enantiomer may have a different equilibrium constant for the inclusion complex formation among the enantiomeric pairs due to the enantioselectivity of the CD. As a result, each enantiomer exists in the aqueous phase at a different time among... 

The keto-enol equilibrium constant of benzoylacetone in water is perturbed in the presence of -cyclodextrin, from a value of 0.62 to 5, and also in sodium dodec-yl sulfate micelles, in both cases by preferential binding of the enol tautomer. Thermodynamic parameters from temperature studies of the equilibrium give more information about the structures of the complexes for example, the enol penetrates further into the cavity of the cyclodextrin, as confirmed by H NMR spectroscopy. Nitrosation of benzoylacetone is slowed in the presence of the cyclodextrin, consistent with a protective effect arising from the strong binding to the enol. 

In seawater, the differences between activities and concentrations must always be considered (cf. Sect. 15.1.1). The activity coefficients for monovalent ions in seawater assume a value around 0.75, for divalent ions this value usually lies around 0.2. In most cases of practical importance, the activity coefficients can be regarded with sufficient exactness as constants, since they are, over the whole range of ionic strengths in solution, predominately bound to the concentrations of sodium, chloride, and sulfate which are not directly involved in the calcite-carbonate-equilibrium. The proportion of ionic complexes in the overall calcium or carbonate content can mostly be considered with sufficient exactness as constant in the free water column of the ocean. Yet, this cannot be applied to pore water which frequently contains totally different concentrations and distributions of complex species due to diage-netic reactions. 

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